Down the DNA Rabbit Hole – Second Cousins

A few weeks ago I noticed a new cousin in my father’s match list at AncestryDNA. The new match was the top person in the third cousin category, an “extremely high” connection sharing 189 centimorgans (cM) over 8 segments. Based on the averages from The Shared cM Project (version 2.0) graph, my father’s newly discovered cousin landed squarely between a range of second cousin (2C) and second cousin once removed (2C1R).

Using Ancestry’s “shared matches” tool, I discovered that our new cousin (whom I will call Fred) also matches my father’s two first cousins on his maternal side, as well as a couple extended cousins on the Foster side of the family. At this point, the additional shared matches have allowed me to narrow down which branches of the tree I should explore. I do these steps before I ever try to contact a match. I like to have an idea of how I am connected to a new cousin to increase the likelihood of having a productive correspondence. How many of us have received generic queries such as “I don’t have any of those surnames in my tree” or “How are we related?” Doing preliminary research saves time and frustration later.

Since Fred matches my father’s first cousins, I checked to see how many centimorgans they share with him. Cousin A shares even more than my father does: 264 cMs across 8 segments. Cousin B shares considerably less: 46 cMs across 4 segments. Such is the randomness of recombination! However, if I average the amount of shared DNA between these three first cousins, the amount is 166 cM. The amount still falls between the average ranges of 2C and 2C1R.

Armed with my growing excitement and an arsenal of data, I contacted Fred. He responded within twenty-four hours! A miracle! And then, I learned, Fred was adopted at birth. He knew only sketchy details of his origins, including the city where he was born. I have heard that some people shy away from matches once they learn a person is adopted, however I provide all the assistance I can. I knew Fred was connected to a specific branch of my family, and relatively closely. Based upon Fred’s information and his DNA test, it is likely that my family was a paternal match, not maternal. If Fred was possibly a 2C or 2C1R, I needed to determine who the potential males of my family tree were at these ranges.

Finding the Second Cousins

Most of us know who our first cousins are. For me, it’s very simple. I can count them all on one hand and still have my thumb left over. I am a little sketchy on how many second cousins I have without my family charts in front of me. I’ve never actually counted them! Both my parents had plenty of first cousins, resulting in many more second cousins for me than first cousins. Going further back up the tree, I needed to know how many second cousins my father actually has. In order to help Fred solve his mystery, I needed a firmer grasp of my tree. For Fred, his DNA was a small needle in a very large haystack. He had no idea where to begin looking to solve his puzzle. Whereas I had several clues and a very narrow field of possibilities.

My father’s second cousins on his maternal side

It turns out that my father has twenty-seven known second cousins on his maternal side. This type of research falls under the category of collateral line research, in my opinion, since one must trace all the descendants of a targeted pair of ancestors. Because Fred’s shared amount of DNA with my immediate family falls between the range of 2C and 2C1R, I also had to consider that Fred was likely the child of one of the second cousins, making him a 2C1R. Fred is closer to my age than to my father’s, so there is a potential generational difference between Fred and my father.

Some Foster relationships in comparison to Fred

Since I did not find any likely candidates for Fred’s father amongst my father’s second cousins, I tried to find as many of their children as possible. This generation would be my third cousins or my father’s second cousins once removed. They were a little more difficult to find as many were born after the 1940 census, but other records (like obituaries) became more useful. So far, I have identified over twenty-five cousins in this group. Of these, one male fits all the criteria, including being in the right place at the right time, to be Fred’s potential biological father. Granted I haven’t tracked down all of the cousins in this group, but I feel fairly confident that we have found a highly probable candidate.

In the future we have several options including: sitting back to wait and see who else tests (just this morning a new known 2C1R on this branch of the family popped up), or be more proactive and solicit one of Fred’s potential half siblings to test.

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5 thoughts on “Down the DNA Rabbit Hole – Second Cousins”

“one male fits all the criteria, including being in the right place at the right time, to be Fred’s potential biological father. Granted I haven’t tracked down all of the cousins in this group, but I feel fairly confident that we have found a highly probable candidate.” Well done! 🙂

I love this! So fascinating. And, I understood it. 🙂 Good luck to Fred. I hope you are able to help him. My aunt learned who her father was at the age of 60. Her discovery came from her Ancestry DNA test results and matching to two half-siblings.